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【2月22・23日】桂智男教授による国際レクチャー等を開催いたします

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2018年2月22・23日に、愛媛大学において、桂智男教授(BGI, University of Bayreuth)による国際フロンティアレクチャーを開催いたします。

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また、23日には国際フロンティアセミナーを開催いたします。詳細はこちら

GRC & MEXT Shin-Gakujutsu “Core-Mantle Coevolution” International Frontier Lecture

日時 2018年2月22(木)-23日(金)9:00 – 16:00
場所 愛媛大学総合研究棟I会議室#486
講師 Prof. Tomo Katsura (BGI, University of Bayreuth)
題目 Physics and Chemistry of the Earth’s mantle
要旨 Basic understanding of physical and chemical properties of mantle materials is essential for investigating the structure and dynamics of the Earth’s mantle. In this lecture, we will discuss the following three topics from various background knowledges necessary for study of the Earth’s interior.
Part 1: Thermochemistry of binary solutions
The major mantle minerals such as olivine, pyroxenes, wadsleyite, ringwoodite, garnet (majorite), bridgmanite, ferropericlase and post-perovskite are ferromagnesian minerals. Therefore, binary chemical equilibrium is vital to understand the structure of the mantle. In this lecture, we will discuss thermochemistry from its basis to equilibrium of non-ideal solutions.
Part 2: Equation of state
Density is an essential parameter to investigate the structure and dynamics of the Earth’s interior. To describe change in density as a function of pressure and temperature, various kinds of equation of states were proposed. In this lecture, we will discuss equation of states frequently used in geophysics for investigation of the Earth’s mantle.
Part 3: Electrical conductivity
Electrical conductivity is a physical parameter of the Earth’s interior that can be remotely estimated from the Earth’s surface. We will discuss electrical conduction mechanism in upper-mantle minerals, and attempt to explain geophysical observation on conductivity structures of the oceanic asthenosphere
問い合わせ A04-1 土屋卓久

The 69th GRC & The 14th MEXT Shin-Gakujutsu “Core-Mantle Coevolution” International Frontier Seminar

日時 2018年2月23日(金)16:30 – 18:00
場所 愛媛大学総合研究棟I会議室#486
講師 Prof. Tomo Katsura (BGI, University of Bayreuth)
題目 Binary phase relations between ringwoodite and bridgmanite + ferropericlase: implication for sharpness of the 660-km discontinuity
要旨 Short wave-length seismic reflections from the 660 km discontinuity indicate that the 660-km discontinuity is extreme sharp, namely less than 2 km thick. Since the Earth’s mantle is considered to consist of ferromagnesian silicates, and the 660-km discontinuity is usually attributed to dissociation of ringwoodite to bridgmanite + ferropericlase, the extreme sharpness of the 660-km discontinuity must be explained by the pressure interval of the ringwoodite + bridgmanite + ferropericlase three-phase regions. However, the thickness less than 2 km corresponds to a pressure interval less than 0.1 GPa. Such a small pressure interval was, however, too difficult to investigate by means of high-pressure experiments. In this study, we have determined the binary loop of ringwoodite + bridgmanite + ferropericlase at a temperature of 1700 K. More concretely, we simultaneously determined transition pressures at Mg2SiO4 and (Mg0.7Fe0.3)2SiO4 compositions by means of in situ X-ray diffraction in a multi-anvil press to estimate pressure difference between the Mg end-member transition and the ringwoodite – bridgmanite – ferropericlase – stishovite four-phase coexistence. Then, we estimated compositional width of the binary loop by means of thermochemical calculation using data available in literature. The striking difference from previous investigations is that the four-phase coexistence is located at higher pressure than the Mg end-member transition at 1700 K. The pressure
difference was found to be 0.14 ± 0.11 GPa. The compositional difference between ringwoodite and bridgmanite + ferropericlase satisfying the observation by in situ X-ray diffraction is 1 mol% at this temperature. this difference becomes smaller with temperature, and virtually zero at temperatures of 2000 to 2300 K. From these investigations, we have concluded that the thickness of the ringwoodite + bridgmanite + ferropericlase binary loop is essentially zero at mantle temperatures, which explains the sharpness of the 660-km discontinuity
問い合わせ A04-1 土屋卓久

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